1. Field of the Invention
This invention relates to a gases supply and gases humidification apparatus, particularly but not solely for providing respiratory assistance to patients or users who require a supply of gas at positive pressure for the treatment of diseases such as Obstructive Sleep Apnea (OSA), snoring, or Chronic Obstructive Pulmonary Disease (COPD) and the like. In particular, this invention relates to a compressor or blower for use in a gases supply apparatus which in use is integral with the gases supply apparatus.
2. Summary of the Prior Art
Devices or systems for providing a humidified gases flow to a patient for therapeutic purposes are well known in the art. Systems for providing therapy of this type, for example CPAP therapy, have a structure where gases at the required pressure are delivered from a blower (also known as a compressor, an assisted breathing unit, a fan unit, a flow generator or a pressure generator) to a humidifier chamber downstream from the blower. As the gases are passed through the heated, humidified air in the humidifier chamber, they become saturated with water vapour. The gases are then delivered to a user or patient downstream from the humidifier, via a gases conduit.
Humidified gases can be delivered to a user from a modular system that has been assembled from separate units (that is, a system where the humidifier chamber/heater and the breathing unit/blower are separate items) connected in series via conduits. A schematic view of a user 1 receiving air from a known (prior art) modular assisted breathing unit and humidifier system is shown in FIG. 1. Pressurised air is provided from an assisted breathing unit or blower 2a via a connector conduit 10 to a humidifier chamber 4a. Humidified, heated and pressurised gases exit the humidifier chamber 4a via a user conduit 3, and are provided to the patient or user 1 via a user interface 5.
It is becoming more common for integrated blower/humidifier systems to be used. A typical integrated system consists of a main blower or assisted breathing unit which provides a pressurised gases flow, and a humidifier unit that mates with or is otherwise rigidly connected to the blower unit. This mating occurs for example by a slide-on or push connection, so that the humidifier is held firmly in place on the main blower unit. A schematic view of the user 1 receiving air from a known, prior art integrated blower/humidifier unit 6 is shown in FIG. 2. The system operates in the same manner as the modular system shown in FIG. 1, except that humidifier chamber 4b has been integrated with the blower unit to form the integrated unit 6.
The user interface 5 shown in FIGS. 1 and 2 is a nasal mask, covering the nose of the user 1. However, it should be noted that in systems of these types, a mask that covers both the mouth and nose, a full face mask, a nasal cannula, or any other suitable user interface could be substituted for the nasal mask shown. A mouth-only interface or oral mask could also be used. Also, the patient or user end of the conduit can be connected to a tracheostomy fitting, or an endotracheal intubation.
U.S. Pat. No. 7,111,624 includes a detailed description of an integrated system. A ‘slide-on’ water chamber is connected to a blower unit in use. A variation of this design is a slide-on or clip-on design where the chamber is enclosed inside a portion of the integrated unit in use. An example of this type of design is shown in WO 2004/112873, which describes a blower, or flow generator 50, and an associated humidifier 150.
For these systems, the most common mode of operation is as follows: air is drawn by the blower through an inlet into the casing which surrounds and encloses at least the blower portion of the system. The blower pressurises the air stream from the flow generator outlet and passes this into the humidifier chamber. The air stream is heated and humidified in the humidifier chamber, and exits the humidifier chamber via an outlet. A flexible hose or conduit is connected either directly or indirectly to the humidifier outlet, and the heated, humidified gases are passed to a user via the conduit. This is shown schematically in FIG. 2.
Impeller type fans or blowers are most commonly used in breathing systems of this type. An impeller blade unit is contained within an impeller housing. The impeller blade unit is connected to a drive of some form by a central spindle. A typical impeller housing is shown in FIGS. 3 and 4. A typical rotating impeller blade unit which in use is located inside the housing is shown in FIGS. 5 and 6. Air is drawn into the centre of the impeller unit through an aperture, and is then forced outwards from the centre of the housing towards an exit passage (usually located to one side of the housing) by the blades of the rotating impeller unit. An impeller blower suitable for use with a breathing system is described in U.S. Pat. No. 6,881,033.
Generally, domestic users receive treatment for sleep apnea or similar. It is most common for a nasal mask, or a mask that covers both the mouth and nose, to be used. If a nasal mask is used, it is common to strap or tape the mouth closed, so that the use of the system is effective (mouth leak and the associated pressure drop are substantially reduced or eliminated). For the range of flows dictated by the user's breathing, the CPAP device pressure generator provides a flow of gases at a substantially constant pressure. The pressure can usually be adjusted before use, or during use, either by a user, or a medical professional who sets up the system. Systems that provide variable pressure during use are also known—for example BiPAP machines that provide two levels of pressure: One for inhalation (IPAP) and a lower pressure during the exhalation phase (EPAP).
A person using a breathing assistance apparatus will inhale and exhale as part of their breathing cycle. As the user exhales, they are exhaling against the incoming gases stream provided by the blower. It is well-known in this field of technology to add a one-way or bias valve to the system, on or close to the mask or interface. A mask vent is described in U.S. Pat. No. 6,662,803. This allows exhaled air to be vented to atmosphere.
A mask vent of different design is described in EP 1275412.
U.S. Pat. No. 6,123,074 discloses a system where the mask includes an exhaust port, and where pressure in the breathing system is constantly monitored and a pressure controller downstream of the flow generator (between the mask and the flow generator) acts to maintain a constant pressure within the conduit.
U.S. Pat. No. 6,526,974 discloses a CPAP device where the size of the inlet to the blower or flow generator can be varied, or where the size of the inlet is automatically varied, in response to the needs of the user. An exhalation path is also provided.
The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.